Ambient pressure responsive switch



United States Patent w AMBIENT PRESSURE RESPONSIVE SWITCH Robert E. Eby,Silver Spring, and William K. Boettinger,

Baltimore, Md., assignors, by direct and mesne assignments, to theUnited States of America as represented by the Secretary of the NavyFiled Feb. 1, 1966, Ser. No. 526,323 4 Claims. (Cl. 200-83) ABSTRACT OFTHE DISCLOSURE A pressure responsive electric switch designed to make orbreak an electric circuit in response to changes in ambient pressure. Apair of pre-set diaphragms and a metallic bellows forms a referencepressure chamber which is acted upon when the desired ambient pres-sureis reached at which a circuit is intended to be completed or broken.Facing contact buttons on each diaphragm, electrically connected,facilitate a making or breaking the circuit depending on the referencepressure and the ambient pressure conditions. The reference pressurechamber is isolated from ambient pressure pulsations and from airimpurities by an attenuator means between the ambient environment and ahousing surrounding the reference pressure chamber.

This invention relates to electrical switches designed to make and/0rbreak an electric circuit in response to changes in ambient pressure as,for example, where the switch is carried aloft by an airborne device inwhich an electric circuit is to be made and/or broken at somepreselected altitude. Such switches may be required to respond quickly,reliably, and with a high degree of accuracy while at the same time theymust be capable of withstanding severe vibrational and gravity stresses,otherwise, the circuit to be controlled may be prematurely made orbroken.

Accordingly, it is an object of the present invention to provideranelectrical switch which will be actuated in response to changes inambient pressure.

Another object of the present invention is to provide a pressureactuated switch for making and/or breaking an electric circuit.

Yet another object of the present invention is the provision ofprotection means for diaphragm type switch elements.

A further object of the present invention is to provide a pressureactuated electrical switch having micrometric adjusting means forchanging the spacing between the switch contacts.

Still a further object of the present invention is to provide a pressureactuated electric switch having means for eliminating any suddenpulsations in the pressure that actuates the switch.

A further object of the present invention is the provision of a pressureactuated switch having a high degree of accuracy and which is immunizedfrom vibrational and gravity stresses.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawingswherein:

FIG. 1 is a side elevation view taken along line 11 of FIG. 2;

FIG. 2 is a top View of the switch taken along line 22 of FIG. 1; and

FIG. 3 is a schematic diagram showing the electrical wiring between thetwo switch elements and the plug mounted in the base.

Referring now to FIG. 1, the switch is shown as Patented Nov. 28, 1967made up of a base 12, two switch elements 14, 16 shock mounted on thebase and a cover or housing 18 having a pressure sensing tube 20. Eachof the switch elements are electrically connected to a coupling means,such as plug 22, for connecting the switch elements into a circuit. Thecover and base make up a housing means having a pressure chamber 24therein and it is the pressure within this chamber 24, as sensed bypressure tube 20, which actuates the switch elements.

Since the two switch elements are identical, only one need be describedin detail. The switch elements have a support structure made up of anupper plate 26 and a lower plate 28 held in substantially parallelspaced relation to each other by hinge pins 30 and by differential screwadjusting means 32. A spring 34 biases the plates apart against theholding action of the differential screw. Each of the plates havecoaxial circular openings 36 for receiving diaphragms.

The diaphragms are made of a material having matched thermalcharacteristics such as, for example, Ni-Span C and are usually formedwith a series of corrugations as shown in FIG. 1. A pair ofhemispherical contacts 38 are fixed on the ends of conductors 40 whichproject through seals 42 made of suitable insulating material.

Each of the diaphragms overlie the circular openings of the plate andare attached at their peripheral or marginal edges to the plate.Dish-shaped protective covers 44 are also attached to the plates andproject through the circular openings of the mounting plates. Each coverhas a. pressure sensing opening 46 and an insulated contact 48 extendingthrough the cover. A flexible electrical connection 50 is made betweenthe contact carried by the diaphragm and the contact carried by theprotective cover. The inner opposed surfaces of the plates are connectedby a flexible wall member in the form of a metallic bellows 52 whichforms a reference pressure chamber 54 around one side of both of thediaphragms. A tube 56 extends from the bellows for pressurizing thereference chamber and which may be sealed after the corrected referencepressure has been established.

The adjustment means for the switch elements is a differential screw 32which enables micrometric longitudinal adjustment for each turn of thescrew. One side of the mounting plates are rigidly attached to hingepins 30 such that the pins are bent by the action of the differentialscrew in raising or lowering the opposite side of the upper plate. Thedistance between the contacts are thus adjusted by the pivotal movementof the upper plate.

Each of the switch elements are attached by screws 57 to base 12. Rubbershock mounts 58 are employed to ensure that the switch elements willwithstand severe vibrational and gravity stresses. The contacts 48 inthe diaphragm protective covers are electrically connected to a fourterminal plug 22 mounted in the base.

As shown in FIG. 3 one contact of each switch element is electricallyconnected to a common terminal 60 and the other contact of each switchelement is electrically coupled to terminals 62, 64, respectively.Terminal 66 is electrically grounded to the switch casing. It will beunderstood, however, that the switch elements may be connected such thatthey operate independent circuits, operate in parallel in the samecircuit, or operate in series in the same circuit.

The housing 18 is sealed to the base member 12 in order to form pressurechamber 24 around the switch elements. A tube 20 extends from theoutside casing to the pressure source which is to operate the switchelements. A filter means 68 connected to the end of tube 20 eliminatesmost of the dust or dirt particles from the inside of the pressurechamber. Two attenuator tubes 70 extend from the pressure tube intochamber 24 and which because of their diameter to length ratio act toeliminate any pulsations in the pressure that is sensed.

In operation, the reference chambers 54 of each switch element arepressurized and the contacts of each element are adjusted by means ofdiiferential screw 32 so that the contacts touch or separate when apredetermined pressure acts upon the dia-phragms. Each switch elementcan be adjusted so as to be actuated at the same or different pressures.The pressure which is to act on the switch element is sensed by pressuretube 20 through filter means 68 and acts within pressure chamber 24 viaattenuator tubes 70. This pressure acts upon the opposed diaphragms ofeach switch element and against the reference pressure in referencechambers 54. When the predetermined pressure within chamber 24 isattained, the contacts of each switch touch each other or separate fromeach other depending upon whether the switch is designed to open orclose the electric circuit into which the switch has been connected.

It should be noted that the protective covers 44 effectively preventaccidental rupturing of the diaphragms by effectively eliminating accessto the diaphragrns except via the small pressure sensing openings 46.Thus, contact with the diaphragm by tools, such as screw drivers, or byany moving object is prevented. Furthermore, the flexible electricalconnection 50 between conductor 48 in the protective cover and conductor40 in the diaphragm allows for unrestricted movement of the diaphragm.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A pressure responsive switch apparatus comprising:

at least one switch element, said element including a pair of opposed,spaced apart diaphragms, -a resilient bellows between said diaphragms,said diaphragm and bellows constituting a reference pressure chamber,means for pressurizing said reference pressure chamber to apredetermined pressure, a pair of coacting contacts carried by saiddiaphragm-s within said reference pressure chamber, said contacts,respectively, being electrically connected through said diaphragms intoan electric circuit;

a housing completely surrounding said switch element so as to form asealed pressure chamber therearound, said switch element being mountedwithin and wholly spaced from the walls of said housing;

coupling means mounted on a wall of said housing for 5 connecting saidcontacts into the electric circuit; and

sensing means mounted on a wall of said housing for attenuatingturbulent pressure within said pressure chamber, said sensing meansincluding a pressure tube exterior of said housing and a pair of attenuator tubes interior of said housing, whereby actuation of said switchelement is effected through said sensing means as the pressure withinsaid pressure chamber acts upon said opposed diaphragms, against thepressure in said reference pressure chamber, and, when the predeterminedpressure within said reference pressure chamber is attained, saidcontacts touch or separate for either closing or opening the electriccircuit.

2. The apparatus of claim 1 wherein said switch element furtherincludes:

a pair of substantially parallel supporting plates each having anopening therein, one of said diaphragms spanning each opening; and

a protective cover secured over each opening for protecting saiddiaphragms from accidental rupture, each said cover having aperturestherein allowing communication between said pressure chamber and theexterior of said diaphragms.

3. The apparatus of claim 2 wherein said switch element further includesmeans for adjusting said plates towards and away from one another to setthe spacing of said contacts.

4. The apparatus of claim 3 wherein said sensing means further includesa filter mounted on the open end of said pressure tube for preventingdust and dirt particles from entering said pressure chamber.

References Cited UNITED STATES PATENTS 2,450,961 10/1948 Heyman et a1.2,582,483 1/ 1952 Hallerberg. 2,671,833 3/1954 Dunmyer et al ZOO-81.5

BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

1. A PRESSURE RESPONSIVE SWITCH APPARATUS COMPRISING: AT LEAST ONESWITCH ELEMENT, SAID ELEMENT INCLUDING A PAIR OF OPPOSED, SPACED APARTDIAPHRAGMS, A RESILIENT BELLOWS BETWEEN SAID DIAPHRAGMS, SAID DIAPHRAGMAND BELLOWS CONSTITUTING A REFERENCE PRESSURE CHAMBER, MEANS FORPRESSURIZING SAID REFERENCE PRESSURE CHAMBER TO A PREDETERMINEDPRESSURE, A PAIR OF COACTING CONTACTS CARRIED BY SAID DIAPHRAGMS WITHINSAID REFERENCE PRESSURE CHAMBER, SAID CONTACTS, RESPECTIVELY, BEINGELECTRICALLY CONNECTED THROUGH SAID DIAPHRAGMS INTO AN ELECTRIC CIRCUIT;A HOUSING COMPLETELY SURROUNDING SAID SWITCH ELEMENT SO AS TO FORM ASEALED PRESSURE CHAMBER THEREAROUND, SAID SWITCH ELEMENT BEING MOUNTEDWITHIN AND WHOLLY SPACED FROM THE WALLS OF SAID HOUSING; COUPLING MEANSMOUNTED ON A WALL OF SAID HOUSING FOR CONNECTING SAID CONTACTS INTO THEELECTRIC CIRCUIT; AND SENSING MEANS MOUNTED ON A WALL OF SAID HOUSINGFOR ATTENUATING TURBULENT PRESSURE WITHIN SAID PRESSURE CHAMBER, SAIDSENSING MEANS INCLUDING A PRESSURE TUBE EXTERIOR OF SAID HOUSING AND APAIR OF ATTENUATOR TUBES INTERIOR OF SAID HOUSING, WHEREBY ACTUATION OFSAID SWITCH ELEMENT IS EFFECTED THROUGH SAID SENSING MEANS AS THEPRESSURE WITHIN SAID PRESSURE CHAMBER ACTS UPON SAID OPPOSED DIAPHRAGMS,AGAINST THE PRESSURE IN SAID REFERENCE PRESSURE CHAMBER, AND, WHEN THEPREDETERMINED PRESSURE WITHIN SAID REFERENCE PRESSURE CHAMBER ISATTAINED, SAID CONTACTS TOUCH OR SEPARATE FOR EITHER CLOSING OR OPENINGTHE ELECTRIC CIRCUIT.